Curling tongs, soldering irons, electric irons, hair dryers and coffee machines may be mentioned, in particular, as apparatuses which can use gas combustion as the heating source. In these apparatuses, there is provided a reservoir containing the combustible gas, in most cases in the liquid phase, a flow regulator/evaporator which guarantees a constant flow of fuel in the gaseous phase, an igniting device and a heat-distributing member permitting optimum utilization of the thermal energy coming from the combustion of the gas/atmospheric oxygen mixture. The presence of the regulator/evaporator, which generally consists of a porous mass whose permeability determines the gas flow, is intended not only to guarantee that the fuel will reach the burner in the gaseous state, but also to limit the flow to a value such that the combustion generates, in the heat-distributing member, an average temperature situated between two limiting values, a lower limit corresponding to the operating threshold of the apparatus and an upper limit beyond which this operation would be dangerous.
The thermal phenomena are generally relatively slow to develop and stabilize, mainly due to the thermal inertia of the constituent elements of the heat-distributing member, each of which has a considerable specific heat, and also due to the size of the heat losses through convection and conduction.
As a result, a not insignificant length of time is necessary for the heat-distributing member to reach the minimum operating temperature.
This time could be reduced by increasing the gas flow, but this would also lead to a rise in the average temperature of the heat-distributing member, which could result in an operating temperature above the maximum safe temperature.